Prominent ear deformity is common amongst the human population. An ear which projects more than 17 mm from the side of the head is usually perceived as prominent. By this estimate, up to 10% of the population may be affected (1-2). It is desirable to correct the prominence very early in life when the cartilage is soft and pliable, however often the prominence is ignored and not treated. Consequently, many children suffer the psychological consequences associated with prominent ears which can persist into adulthood. Therefore there is a need to develop a safe and effective method for correction which can be used in both adults and children.
The ear cartilage is cup-shaped and is formed of the conchal fossa and the antihelical fold which allows the ear to lie flat against the side of the head. Prominence may result in the abnormal formation of the antihelical fold, or folded over rim (FIGS. 1b and 2a) during embryonic development. Alternatively, it may be the result of a deep conchal fossa (FIG. 2b). One or both of these abnormalities may need to be addressed when correcting prominence of the ear. However, even for ears with a deep conchal bowl, accentuation of the antihelical fold will make a difference to the perception of prominence(1). In most cases the prominence is apparent at birth but can develop soon afterwards and in some cases up to the age of five.
There are a number of known methods for addressing the problem of prominent ears such as otoplasty surgery and non-invasive methods involving the application of devices or splints to the exterior of the ear.
Surgical techniques, for example otoplasty or pinnaplasty, are available to change the shape of the ear and correct the deformity. These vary from very invasive procedures to reshape the cartilage to minimally invasive procedures, for example percutaneous scoring of the cartilage(3). The principle involved in all of these procedures is reshaping of the cartilage which gives the ear its prominence. However, otoplasty is a lengthy procedure taking approximately 45 minutes for each ear. In addition a number of problems and complications are associated with this type of surgery and with percutaneous scoring of the cartilage(3-6) such as infection, bleeding, skin necrosis, death from general anaesthesia, recurrence of the prominence, keloid or hypertrophic scarring, asymmetry, palpable sharp edges (where the cartilage has been cut), pain, numbness and cold intolerance/sensitivity.
The use of minimally invasive techniques using needles or similar instruments overcome some of the above-identified problems, have fewer complications and take less time, for example 15 minutes per ear. However, such techniques have the disadvantage in that they are less successful in achieving the desired prominence correction and have a higher rate of asymmetry and the formation of palpable sharp edges compared with standard otoplasty surgery.
Furthermore such surgical techniques, both invasive and minimally invasive, require substantial training and experience. In general the results of the first 10-20 cases are likely to be unpredictable (6). To overcome the problems associated with surgical otoplasty and minimally invasive methods several known devices are in use to correct the deformity and avoid surgery altogether. These are essentially external splints which deform the cartilage by the continuous application of external force.
One such device, known as Earbuddies™ is formed from a piece of soft wire coated in silicone (for comfort) which is moulded and placed onto the outside of the ear and taped into position. The cartilage moulds its shape to that of the ear buddy and any prominence is corrected. At birth and for a variable time afterwards (up to six months), the cartilage of the human ear remains soft and deformable. Therefore, external forces applied to the cartilage can result in permanent changes to its shape(7-8). Hence, Earbuddies™ have most success in children up to the age of six months, after this age the cartilage becomes firmer and more resistant to deformation. Also the increasing dexterity of the child who will try (and usually succeed) in removing the splint reduces its effectiveness.
Another device, Aurimethod™ which includes the use of the Auri®Clip and Auri®Strip devices applies gentle, continuous, external pressure to the cartilage of the ear in the region of the antihelical fold. This deforms the cartilage in this area over a prolonged period of time to make the ears lie flatter against the head. The Auri®Strip is a very thin (0.2 mm thick), transparent and double-sided medical adhesive material that is invisible when worn and can also be used to reshape the antihelical fold. It is claimed that 3 to 6 months treatment is enough to have a permanent effect.
The disadvantage of this method is skin irritation and compliance which reduced the overall success rate (9).
WO2007/023296 discloses surgical scaffolds formed of shape memory material for use in reshaping the cartilage of the nose or the ear. One, two (or three) of the implants (FIG. 3) are inserted subcutaneously into the ear as shown in FIG. 3c. On insertion, the implant is embedded in the cartilage and released. Upon release, the implant changes from one shape to a second pre-programmed shape which results in an instant change in the shape of the underlying cartilage.
These scaffolds have a reduced risk of complications and time taken to recover from the treatment and have therefore overcome a number of the problems associated with standard otoplasty and minimally invasive otoplasty surgery. However, such devices often do not produce the desired change in shape of the anti-helical fold and although the anti-helix does fold, it is not always in a predictable manner to produce the optimal curvature. In addition these scaffolds often have a poor conformance to the cartilage and sit ‘proud’ which can compromise the correction of prominence. Therefore there is a need to further improve the attachment and fit of the scaffold to the cartilage to achieve reliable results.
Furthermore these scaffolds are designed to fit the average dimensions of the human ear, and as such are not suitable for all ears which are infinitely variable. Furthermore, there is a need to improve design and materials such that insertion and removal are minimally invasive.
Due to the size of the introducer on which the scaffold is held, it is necessary to make a corresponding incision that will accommodate the introducer such that the scaffold can be correctly positioned in place. This has the disadvantage that recovery time is longer due to post-surgical effects such as pain and bleeding. In addition, further surgical intervention is necessary to remove the scaffold once correction has been effected due to the visibility of the scaffold under the skin. Also, these scaffolds are not suitable for long term or permanent use.
Whilst the suitability of Nitinol scaffolds has been established for use in correcting ear deformities there remains a need to further improve the design of the scaffolds such that insertion and removal are minimally invasive and the method of insertion is simpler requiring less time and surgical skill. In addition, a design with lower visibility has the advantage that removal is not necessary in cases where deformity is not permanently corrected after treatment, or if the scaffold is to be removed, this will be required less often.
Thermoplastics are polymers capable of undergoing a reversible transition from a relatively hard brittle state to a molten or rubber-like state. The temperature at which this occurs is known as the glass transition temperature (Tg). Thermoplastics can undergo repeated melting/cooling cycles and can be re-shaped on heating. Known thermoplastics include polyethylene, polypropylene, polystyrene, polyester, polyvinyl chloride, acrylics, nylons, spandex-type polyurethanes and cellulosics.
The thermoplastic polymers manufactured by Inion Oy, Finland, have been used successfully in bone regeneration(10) and are biodegradable. The polymers degrade in vivo by hydrolysis within 12 months to form carbon dioxide and water(11). The polymers are commercially available in the form of pre-cut strips or as plates from which the desired shape and size can be easily cut.
It is an object of the present invention to provide an improved ear scaffold which overcomes the above-mentioned problems and demonstrates improved predictability and efficacy.